The present invention relates to a device for controlling the power of an internal combustion engine by means of a throttle valve which is rotatably mounted in an intake pipe of the engine, wherein a displacement of the throttle valve is effected by an electromotive actuator in the idle range and by a gas pedal via a cable and a pulley in the driving range.
In such devices it is generally desired to obtain the the most linear possible increase of the air throughput, m, as a function of the adjusted angle, .alpha., of the throttle valve in the lower, air flow part of the control range.
For this purpose, it has been proposed to divide the throttle valve in two parts and to turn the two parts independently of each other (German A 29 50 866). Such construction is very expensive and trouble-prone and it has not been able to gain acceptance.
In accordance with another proposal (German C-34 03 760), a pulley which is developed as a cam plate provides that, for the same distance as displacement of the gas pedal, the change in the angle of the throttle valve is considerably less in a lower part of the control range than in an upper part of the control range.
Finally, it has also been proposed to adapt the inner contour of the intake pipe to the path of swing of the throttle valve such that there is less change in the cross section of flow in the lower control range than with a purely cylindrical inner contour of the suction connection (France A-22 34 497). With this method, which is somewhat more expensive from a manufacturing standpoint, it is possible to obtain curves m=f (.alpha.) which are as flat as desired. As a result, there is a reduction in the maximum mass of air which can be passed through because the change in the inner contour cannot be obtained without a reduction in the cross section of flow. Furthermore, the curve m=f (.alpha.) has a bend at the place where the throttle valve comes out of the adapted inner contour. The reduction in the maximum air throughput can be compensated for by an increase in the total cross section and the bend can be mitigated by additional measures.
However, it has been found intolerable that the flat characteristic curve m=f (.alpha.) which is achieved with reference to a sensitive idle regulation by the electromotive actuator drive is accompanied by unsatisfactory acceleration behavior when the control of the power is taken over by the driver. In other words, in the lower control range, too large a pedal path is required in order to obtain the given effect. Basically, there is a conflict between the most economical manner of driving and a forceful style of driving which fully utilizes the power of the internal combustion engine. This conflict could be resolved in favor of economy and the control device could be developed technically in corresponding manner if the development of full power were not required at times in order rapidly to pass another car. In the same way as in the kick-down control of automatic transmissions, it is necessary, in the case of a control device with a flat course of the characteristic curve, to have a possibility of action in order to be able to again have the entire power of acceleration of the internal combustion engine.